Abstract: A method for hardening gelatin which comprises using as a hardening agent a compound represented by formula (I): ##STR1## wherein R.sub.1, when taken along, may be alkyl of 1 to 20 carbon atoms, aralkyl of from 7 to 20 carbon atoms, aryl of from 6 to 20 carbon atoms, and alkenyl of from 2 to 20 carbon atoms. R.sub.1 and R.sub.2 can also combine with each other to form a heterocyclic ring of 5 to 8 atoms. The R.sub.1 -R.sub.2 ring contains the nitrogen atoms to which R.sub.1 and R.sub.2 are attached, and may also contain an additional nitrogen atom. R.sub.2 and R.sub.3 can combine to form either a 5 or 6 membered ring. The R.sub.2 -R.sub.3 ring contains the nitrogen atom to which R.sub.2 is attached, and may also contain one or two additional nitrogen atoms. R.sub.4 may be hydrogen or alkyl of 1 to 4 carbon atoms. R.sub.

Abstract: In a Mach-Zehnder electro-optic modulator (10), an optical waveguide (14) includes two branches (20,22) extending between an optical input (16) and an optical output (18) is formed in a substrate (12) of a material having electro-optical properties. An electrical signal applied to a modulation input (34) affects the material such that the effective optical lengths of the branches (20,22) vary differently in correspondence with the magnitude of the electrical signal. The optical signals propagating through the branches (20,22) interfere with each other at the optical output (18) at a phase angle depending on the difference between the effective optical lengths. A selected electrical bias voltage applied to the modulation input (34) causes non-linear modulation of an input optical signal with one or more even integral multiples of an electrical input signal which is additionally applied to the modulation input (34), thereby providing frequency multiplication.

Abstract: A method for hardening gelatin comprising combining the gelatin to be hardened with a compound of the formula: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, and X.sup..THETA. are as herein defined. The compounds of this formula effectively harden gelatin with little or no after-hardening. These compounds are useful in hardening gelatin in photographic elements.

Abstract: We have found that transistors have desirable device characteristics when the base region is composed of a lightly doped layer near the emitter junction and a heavily doped layer near the collector junction. The edge of the depletion region at the emitter-base junction is designed to stop in the lightly doped base region.

Abstract: Useful field effect transistors can be made with gallium indium arsenide as the electron conducting layer (channel layer) by incorporating a layer of gallium arsenide for the Schottky barrier. Relatively thick gallium arsenide layers are used to achieve low reverse leakage currents.

Abstract: A modulation-doped field effect photodetector has a fast response time.

Abstract: A new technique called stop cleaving permits semiconductor lasers having etched mirrors to be fabricated on a common substrate with other optical or electronic components such as photodetectors and field-effect transistors.

Abstract: A high speed bias-free photodetector which capacitively couples the output signal to an external circuit is described.

Abstract: A majority carrier photodetector has high sensitivity and fast response times. The photodetector comprises a thin highly doped layer surrounded on either side by two nominally undoped layers which are completely depleted at thermal equilibrium.

Abstract: A thin and highly doped Ga.sub.0.47 In.sub.0.53 As layer disposed on a Ga.sub.0.47 In.sub.0.53 As layer increases the barrier height and produces useful device characteristics. For example, the structure may be used as the gate electrode in an InGaAs field effect transistor.

Abstract: Novel electron donor precursors have the structure: ##STR1## where: R is an alkali labile group;Y is an aliphatic or aromatic group; andZ is an electron withdrawing group.The compounds are useful in photographic elements, film units and processes to provide electrons to immobile compounds which must accept at least one electron before releasing a diffusible dye or photographic reagent.